Electron velocity modulation device



April 4, 1950 s. G. TOMLIN ELECTRON VELOCITY MODULATION DEVICE 2 Sheets-Sheet 1 Filed March 26, 1945 FU/GZ FIG].

I nventor STmuEY QOR ONTOV\L\N A Home April 4, 1950 s. G. TOMLIN 2,502,492

ELECTRON VELOCITY MODULA'I-ION DEVICE Filed March 26, 1945 2 Sheets-Sheet 2 FIG] B Z Altorne i Fig. 6 shows a side View: o fsa I tion device similar to-thoseshownin the previ- ,case'taken at the line 1-1 of Fig. 6.-

Patented Apr. 4, 1950 mn 1 --sm-Es PATENT OFFICE I' Q i Q 2,502,492 u ELECTRON VELOCITY MODULATION DEVICE Stanley Gordon-Tomlin, Aldwych, London, England, assignor, by mesne assignments, to International Standard Electric Corporation, New 7 York, N. Y., acorporation of Delaware Application March-26, 15 15, Serial No. 584,903 I In GreafBrltain March 28, 1944 The" present invention for focussing the electron relates to electron dis-' charge de'vicesof the electron velocity-modula- I 7v clam... (Cl. 315- 5) The invention will be described in relation to a particular type of velocity modulation device,

though the same principles are also applicable to exercise some care-in aligning, the .focussing magnetic:tieldv with the electronbeam: so that the maximum'number of electrons emitted from the cathode may be eifecti-vely utilised.

I It is inecessary also to provide for conveniently 1. replacing such devices in apparatus where they; are used, andit is very troublesome, if- 'notim-t' practicable, to have to carry out aligningf operation every timeone of the devices is' changed or replaced,,since such an requires skill, and test means.

The object of the present invention; therefore,

is to providemeans whereby such devices vmay operation be replaced in the apparatus in such manner;

as to be automaticallycorrectly respect to the focussing field.

The electron velocity modulation devices-with which this invention is concerned will be called for convenience velocity modulation devices,

placed with" and are of the well known kind in whichlaan I electron beamv is directed through'pairs ofg electrodes connected to a resonating system or systems and constituting a gap in which the electron velocities are modulatedandalso a gap in. which energy may be extracted from the beam, with a drift space between the: gaps. Such a device may be an amplifier, modulator, or generator, according to the circumstances of its operation. The, invention will be illustrated-by a specific embodiment shown'on the accompanying drawingsinwhichm g Fig. 1 shows diagrammatically part of velocity modulation device having -a,disc sealed through the envelope; e

Figs. 2 and- 3 show side andend views respec-- tively, of an electrical wave apparatus including a velocity modulation device of the kind shown in Fig.1; Fig. 4 shows locating holes in the disc of the a jig f orpunching the locating holes Fig. 7 showsa sectional view-oiithe device-and to other types, thedetails being modified to suit the particular features of the device concerned. The device in the present case is assumed to be one in which a co-axiai line resonator is excited by an electron beam projected across it, such as is described-in'U. S. Patent No. 2,320,860; In the present case, as indicated diagrammatically in Fig. 1, the tubular resonatorlis encloseclin a glass envelope 2 *through the walls of which. is sealed an annular metal discs integral with the resonator inside, and forming a terminating flange for the resonator. Theenvelope is shown broken away at the left-hand side and is supposed to continue to a suitable base with terminals not shown, and to contain a press also not shown from which the cathode d and target '5 are supported. Electrons are fired across :the resonator i from the cathode 4 to the target 5 ;for the purpose of exciting the resonator.

will be understood that Fig. 1 is not intended to illustrate the device in any detail since 'it is of a well known type, but the figure is principally used to show the relation between the resonator and the disc. p y v :The focussing magnetic field is directed parallel to the electron beam by a magnet external to the device. Figs. 2 and 3 show one way in which the velo city modulation device may be coupled to a coaxial transmission line, for example, which may form part of an apparatus or system. The outline of part of 'theenvelope 2 of thedevice is shown, and the end of the envelope extends into a metal tube '6 having a flange 23 which, may constitute the outer conductor of a coaxial transmission line. The disc 3 of the deviceis 'clamped between the flange 2 3 and .a' plate 8. The plate 8. has a :U-shapedslot-at 9 wide enough to accommodate the envelope of the device.

holes 12 and i3 the disc 3,- shown in Fig. 4,

andinto other holes in the plate 8.

- The central conductor ll of the transmission .line may be coupled'to the central conductor of the coaxial lineresonator I by means of a small condenser plate 48 sealed through the envelope '2, and explained in the specification of co-peiid ingapplication 636,018.- I A focussing magnet I4 is adjustably fixed to the plate '8 by means of a clamping plate L5 and screws 16.

Fig.- 5 showsbne method of punching the .1

not shown I modulation device of the kind described with ref-" l erence' to Fig. 1, complete except for the punching of the holes, is inserted" in the jig with the disc 3 clamped loosely between theplate 8A and the die l9.

A suitable socket not shown vconnected to a test circuit isfixed on the base 22 of the device. This test circuit should include the 'means for generating -.:thee. ectron-beam under the specified conditions and for. measur--, ing the current flowing to the target 5. The deand then a slightly difierent method of locating the deviceispreferable. Referring to Figs. 6 and '7, the protective case comprises a metal tube 24 having a flange 25 at the upper end. Theupper'part of the tube is cut away on either side as-indicated in Fig. 6 so as to form a pair of diametrically'opposite tongues 26, of which :onlyr-onqmn be seen in Fig. 6, connecting the Flower. part of the tube 24 to the flange 25, which vice is then rotated about its axis with" respect to the magnet until amaximum beam current is obtained. This indicates that the maximum number of electrons are fixed through the resonator. The plate 8A and die l9 are now firmly clamped and the punches 20, and 2| are driven through the disc thus making the desired holes.

In this way a marker line is defined by the two holes related to the direction of the electron beam in the same particular manner determined by the focussing test, in all the velocity modulation devices.

r d The next step in the orocess is to fix the magnet M in all specimens of the apparatus with which the velocity modulation device is to be used. It is found that the effective direction of the magnetic field is somewhat variable in dif ferent magnets manufactured to the same specification. Accordingly a standard sample of the velocity modulation device with the two holes punched in the disc is inserted in each apparatus in the manner explained with reference to Figs. 2 and 3, and the test circuit is connected to the base as before. The clamping screws l6 are loosened, and the magnet 14 is then adjusted until a maximum beam current is obtained. The clamping screws H; are then tightened.

" This having been done, any velocity modulation devices with the holes punched in the manner' described can be inserted in the apparatus and will take up the proper position automatically without the necessity for any aligning tests,

so long as the magnet 14 is not afterwards moved.

In order to allow for slight manufacturing differences in the distance between the two pins l0 and H in different samples of the apparatus, one of the holes/for example l3, Fig. 4, may be slightly elongated radially.

It will be seen that if the two holes are punched diametrically opposite to one another, there will be two possible positions for the device in the apparatus differing in orientation by 180. It may be found that these two positions are not equally good in all devices, so in order to ensure that the best position is selected, one of the two holes and the corresponding locating pin may be made larger than the other, or a third hole and pin may be provided, or the two holes [2 and 13 may be punched so that they are angularly spaced by less than 180", or so that they are at difierent distances from the centre. If a third hole and pin are used the three holes should, 'of' course, be unsymmetrically arranged so that there is only one possible position in which all the pins and holes can register. The third hole could be rather larger than its pin, 50 that accurate registration in the case o'fthis' hole is rendered unnecessary.

thus assumes practically the form of an annular disc. Inside the lower -end of the tube 24 is secured in any suitable way a base 22 of insulating material carrying the usual pin terminals for the velocity modulation device. The envelope 2 0f the device'is inserted into the tube 24 and the lead-out wires 21 are threaded through the pin terminals and soldered thereto in the usual way. These wires should .be left sumciently long to allow the device to be rotated through a moderate angle inside the tube 24.

The disc 3 of the velocity modulation device rests upon the flange 25 and is clamped thereto by an annular disc or plate 28 having a central hole large enough to clear the upper part of the envelope 2. The disc 28 is'of somewhat larger diameter than the fiange'25 and is fixed thereto by screws 29. 1

Suitably placed locating- 11016530 are already drilled in the disc 28. A test jig arranged similarly to Fig. 5 is provided, but with fixed locating pins instead of the punches 20 and 2| adapted to engage the locating holes 30. The screws 29 are loosened sufficiently to allow the velocity modulation device to be rotated insidethe tube 24 until a maximum beam current is measured as before. The screws 29 are then tightened.

The apparatus Figs. '2 and 3 will be provided with locating pins corresponding to the holes 30,

and the focussing magnet l4. may be adjusted in the manner already explained. It will be understood that the tube is cut away at the upper "end'in themannerdescribed in order to allow the poles of the magnet closely to approach the envelope -2 in the neighborhood of the electron beam. The disc 28 need not be larger in diameter than the flange 25, and the locating holes 30 could be arranged anywhere therein, but they should not overlap the disc 3 of the velocity modulation device. If they should overlap the flange 25, then, if desired, corresponding locating or clearance holes may-be drilled in this flange to allow the locating pins to pass through both th disc and the'flange.

The locating holes 3!! may be arranged, di-

mensioned, and spaced in any of the ways suggested for the locating holes such as I2 and I3 'punched'in the disc 3' ofthe velocity modulation device, in order to ensure that the device can only be placed in one position the'apparatus in which it is used.

' ""When' the adjustment of the device inside the modulation devices according to the invention are not necessarily constructed in the forms which have been chosen to illustrate the invention. In particular, they may not have any such disc as 3 sealed through the envelope. In such cases, other locating means capable of defining a marker line related in a definite way to the direction of the electron beam must be devised.

Thus, referring to Fig. 5, a velocity modulation device having no disc might be fixed in position by means of an annular clamp grasping the circular base 22. This would allow the velocity modulation device to be rotated with respect to the magnet MA into the proper position. A radial hole drilled into the base 22 would then provide a marker radius related to the direction of electron beam. A corresponding locating pin associated with the annular clamp provided in the apparatus corresponding to Figs. 2 and 3 would then fix the position of the device, the magnet 14 being, of course, adjustably fixed with reference to the clamp so that it can be rotated about the axis of the device. Clearly two or more radial holes with corresponding pins could be used to define a marker line with respect to the electron beam. Other like arrangements can clearly be devised according to the same principles for other type of device. locating hole can only be used if the position of the axis of the device is otherwise determined, so that the hole in this case also effectively defines a marker line which is the radius drawn from the axis to the hole.

What is claimed is:

1. An electrical apparatus for generating ultra high frequency oscillations comprising an envelope enclosing an electron discharge device of the velocity modulation type, said discharge device including a cavity resonator and means for generating an electron beam, means about said envelope for focussing said beam in a beam path through said resonator, and locating means between said focussing means and said discharge device for locating said devicein a definite position with respect to said focussing means, said locating means including means connected to said discharge device for defining a particular marker line thereon whereby a maximum number of the beam electrons are always focussed to be effectively utilized.

2. Apparatus according to claim 1 in which said discharge device includes a metal disc sealed through said envelope in a position parallel to said beam path and said marker defining means includes locating holes in said disc in a definite position with respect to said beam path.

3. Apparatus according to claim 2 in which said locating means includes a protective case mounted about said envelope and provided with apertures for said focussing means, a plate connected to said case and provided with additional locating holes aligned with said locating holes in said disc, and adjustable clamping means clamping said plate and said disc and said focussing means.

It should be noted that a single 4. An apparatus according to claim 3 in which said cavity resonator comprises a coaxial line type resonator, said disc being of annular shape and attached to said resonator at one end forming a terminating flange therefor.

5. An electrical apparatus for generating ultra high frequency oscillations comprising an envelope enclosing an electron discharge device of the velocity modulation type, said discharge device including a cavity resonator and a metal disc connected to said resonator and sealed through said envelope and means in said envelope for generating an electron beam, a magnetic focussing means mounted about said envelope for focussing said beam in a beam path through said resonator in a direction parallel to said disc, said disc being provided with locating holes there in in a definite position with respect to said beam path, and mounting means between said magnetic focussing means and said disc in said holes for locating said magnetic focussing means in a definite position with respect to said beam path whereby a maximum number of the beam electrons are always focussed to be effectively utilized.

6. Apparatus according to claim 5 in which said disc is provided with two diametrically opposite locating holes, one of said holes being larger than the other.

'7. An electrical apparatus for operation with an electron beam comprising an electron discharge device including a cavity resonator, means for generating an electron beam and an envelope enclosing said beam generating means and at least a portion of said resonator, means about said envelope for directing said beam in a path through said resonator, and locating means between said directing means and said envelope for locating said focusing means in a definite position with respect to said beam generating means, said locating means including means connected to said discharge device for defining a particular marker line thereon whereby a maximum number of the beam electrons are always directed to be effectively utilized.

STANLEY GORDON TOMLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,542,366 Brough June 16, 1925 1,765,487 Huffman June 24, 1930 2,000,570 Nina May 7, 1935 2,128,231 Dallenbach Aug. 30, 1938 2,235,527 McArthur Mar. 18, 1941 2,423,819 Chevigny July 8, 1947 FOREIGN PATENTS Number Country Date 9,233 Great Britain May 18, 1909 

